Plastic has taken the place of other materials in a variety of industries. In the packaging industry, plastic has replaced glass to minimize breakage, reduce weight, and reduce energy consumed in manufacturing and transport. In other industries, plastic has replaced metal to minimize corrosion, reduce weight, and provide color-in-bulk products. Recently, an entire industry has arisen called “wood polymer composites” (WPC).
Wood polymer composites are based on the premise that use of biofiber, such as wood fiber and other naturally occurring particulates, as additives to thermoplastic compounds can simulate the appearance of wood while also providing the durability of plastic. Outdoor decorative and structural wood building materials, such as decking, railings, windows, etc. are being made from WPC materials, with and without capstock outer layers.
The ability of the WPC material to simulate the appearance of the natural wood, including its surface texture and wood grain coloration is key to value of the WPC to successfully replace the natural wood itself. Moreover, use of common wood fiber, such as pine, to simulate the appearance of exotic wood is environmentally friendly.
The art has attempted, without success, to provide WPC materials wherein the wood content of the WPC exceeds 50 weight percent.
U.S. Pat. No. 6,498,205 (Zehner) discloses a dry blend of thermoplastic material powder and cellulosic material of about 50% by weight.